Cells from many sources secrete proteins which perform diverse functions in the extracellular environment. However, it is unknown how a cell recognizes what is to be secreted and how the protein traverses the plasma membrane. Several lines of evidence suggest that to be secreted the polypeptide chains undergo conformational changes which may be brought about by various agents. Eucaryotic secretory products are almost invariably glycoproteins, and so the covalently bound carbohydrate may play a role in secretion. The long range goal of this proposal is to determine what biochemical, physiological, and genetic elements influence and control the secretory process. This investigation will be carried out using the fungus, Aspergillus fumigatus which is easily cultured, is amenable to genetic analysis, and secretes several glycoproteins. The glycoproteins, both intra- and extracellular forms, will be purified, their enzymatic and physical properties determined, and the composition and structure of the oligosaccharide side-chains examined. Components of the medium required for glycoprotein synthesis and secretion to take place will be analyzed. Mutants will be selected which are unable to secrete one or more of the glycoproteins and/or to glycosylate the proteins normally, to determine what cellular structures and functions are required for secretion.